Cathode sleeve with flanges crimped against ceramic disc



1965 T. J. HIPSZER ETAL 3,183,394

CATHODE SLEEVE WITH FLANGES CRIMPED AGAINST CERAMIC DISC Filed July :51.1961 IOC mum HA IOS IOS United States Patent 3,183,394- CATHQDE SLEEVEWITH FLANGES CED AGAINST CERAWC DISC Thomas J. Hipszer, Trappe, andNorman Royle, Norristown, Pa, assignors to Superior Tube Company,

Norristown, Pa., a corporation of Pennsylvania Filed July 31, 1961, Ser.No. 128,127 3 Claims. (Cl. 313270) This invention relates to cathodeassemblies such as used in cathode ray tubes and in other types ofthermionic tubes using indirectly heated cathodes.

An extensively used cathode assembly, of type shown in Briggs Patent2,551,871, comprises a thin walled metal sleeve extending through aceramic disc. In the assembly operation, the sleeve is embossed to formbeads or flanges which are crimped or flattened against opposite facesof the disc adjacent the ends of the hole through which the sleeveextends. In production runs of cathode assemblies of this type, a commonproblem is the occurrence of loose fits permitting relative rotationbetween the sleeves and some of the ceramic discs. Such loose fits occurbecause of the practical impossibility of manufacturing the ceramicdiscs with precise uniformity of hole and thickness and because of theeconomic unfeasibility of inspecting every disc before assembling itwith a sleeve. As incorporated in a tube, an assembly with disc capableof rotation with respect to its supporting disc is responsible forincreased microphonics and unstable cut-ofi characteristic. It has beenfound in practice that if the crimping pressure is increased to insurethat there are no loose sleeves then a substantial number of theassemblies must be discarded because of cracked discs, whereas if thecrimping pressure is reduced to avoid breakage of discs then there areinevitably a number of cathode assemblies with loose sleeves which ifnot detected and discarded before incorporated in tubes will result indegraded tube performance.

In accordance with the present invention, the problems of loose fits andcracked discs are solved by providing at least one surface of the discwith spaced grooves extending outwardly from the sleeve-receiving hole.The grooves may be formed in the molding of the discs or they may beformed by grinding the molded discs: in either case the depth of thegrooves progressively decreases outwardly from the sleeve-receiving holeand the groove width may be constant or also progressively decreaseoutwardly from the sleeve-receiving hole. During the crimping operation,the bead or flange of the sleeve is locally deformed into these groovesso keying the sleeve to the disc in prevention of any tendency to rotateshould there be a loose fit. With such grooved disc construction, thecrimping pressure may be preset to a value which insures that allsleeves are firmly held against rotation in their discs and withoutbreakage of slightly thicker discs during the crimping operation.

The invention further resides in cathode assemblies and methods ofmaking them, having novel and useful features hereinafter described andclaimed.

For a more detailed understanding of the invention, reference is made inthe following description of preferred forms thereof to the accompanyingdrawings in which:

FIGS. 1A, 1B and 1C are plan views of grid-cathode spacer discs havingspecifically hole and groove arrangements;

FIGS. 2A and 2B are elevational views, in section, taken on line 22 ofFIGS. 1A and 1B;

FIGS. 3A and 3B are elevational views in section taken on line 33 ofFIG. 1C;

FIG. 4 is a sectional view of a disc and sleeve assembly at a crimpingstation; and

FIGS. 5 and 6 are elevational views, in section, of cathode assembliesmade from the grooved discs of FIGS. lA-lC.

Referring to FIG. 1A, the spacer disc 10A is provided with a triangularhole 11A dimensioned to receive a cathode sleeve or shank 12 indicatedin dotted outline. Each of the three symmetrically spaced grooves orslots 13 extends radially outwardly from the hole 11A at a region ofengagement between the disc 10A and the sleeve 12. Either or both facesof disc 10A may be grooved as respectively shown in FIGS. 2A and 23Referring to FIG. 1B, the spacer disc 10B is provided with a trefoilhole 11B whose central portion defined by lands 15 is dimensioned toreceive the cathode sleeve 12 indicated in dotted outline. Each of thethree symmetrically spaced grooves 13 extends outwardly from the centralportion of hole 118 and radially of a corresponding land 15. Either orboth faces of disc 10B may be slotted or grooved as respectively shownin FIGS. 2A and 2B.

Referring to FIG. 1C, the spacer disc 10C is provided with a circularsleeve-receiving hole 11C of diameter corresponding with the sleevediameter. As shown in FIGS. 1A and 18, each of the symmetrically spacedgrooves 13 extends radially outwardly from the sleeve-receiving hole.Either or both faces of disc 10C may be grooved and the number ofgrooves per face may be upwards of three. When a single face is groovedor when the grooves of one face are offset with respect to the oppositeface, the disc section is as shown in FIG. 3A: when both faces aregrooved and the grooves of opposite faces are in alignment, the discsection is as shown in FIG. 3B.

For small cathode-ray guns and tubes, the spacer discs of FIGS. 1A, 1Band 1C are made in various sizes ranging from 0.25 to 0.5".

In all of the figures of the drawing, the size of the grooves isexaggerated for clarity of illustration; in practice, a width of about0.02" to 0.035 and a depth of about 0.01" to 0.015 affords reliablekeying of the sleeve when its embossed flange 14 (FIGS. 5 and 6) iscrimped or flattened as later described in connection with FIG. 4. Thesleeve 12 is usually of nickel or nickel alloy, and in a typical casemay have a wall thickness of about 0.002" or 0.003" with the flattenedflanges 14 extending about 0.01 to 0.02" beyond the periphery of thesleeve. As indicated in FIGS. 1A and 2A, the groove width may beconstant with depth decreasing outwardly from the sleevereceiving holeof the disc: or as indicated in other figures, both the width and depthof the grooves may decrease outwardly from the sleeve-receiving hole.When, as is usual, the discs are of lava or like refractory insulatingmaterial, the grooves may be, and preferably are, formed during themolding operation or they may be later formed by a grinding operationusing a Wheel of small diameter and appropriately shaped edge.

The radial grooving of the spacer discs is effected prior to theirassembly with cathode sleeves to form cathode assemblies laterassociated with a heater and other electrodes of a cathode ray or otherthermionic tube. Assembling of the sleeves and discs involvessleeveembossing and crimping operations such as disclosed in theaforesaid Briggs patent. Briefly, after an assembly has been partiallyformed by embossing a sleeve to form a pair of beads or flanges onopposite sides of the associated disc, the opposite projecting ends ofthe sleeve are inserted (FIG. 4) within the bores of a pair ofaxially-aligned die members 1616. In a subsequent cycle of operation oftheir press, the dies are brought toward Patented May 11, 1965 I oneanother to flatten the annular flanges 14 against opposite faces of theinterposed spacer disc.

During this crimping operation, the metal flange is locally depressed orexpanded into the grooves 13 so providing a series of flange keyslocking the sleeve against rotation even though the unembossed sleevemay be a loose fit in the sleeve-receiving hole of the spacer disc. Thislocking engagement is maintained during the expansions and contractionsof the sleeve incident to intermittent use of the tube in which thecathode assembly is later incorporated. There is thus avoideddegradation of tube performance which results when a cathode can rotatein its spacer disc.

It has been found in practice that even when only one face of the discsis grooved, FIG. 6, such locking engagement is reliably and reproduciblyobtained with discs differing slightly in thickness and hole size withinfeasible tolerance limits of manufacture. The thickness tolerance may be$0.005" and the hole tolerance within +0.005 and preferably notexceeding +0.002". In fact, when both sides are grooved, the lockingengagement usually 'occurs on only one side of the disc: grooving ofboth sides, however, has the advantage that it is not necessary toorient the assembly in the crimping press.

Although a single groove in one face of the disc can provide a lockingengagement between the sleeve and disc, there is a possibility thatbecause of the dissymmetry of crimping strains in the sleeve, the faceof the subsequently attached cathode cap 17 will not remain perfectlyparallel to the disc. With a symmetrical arrangement of three or moregrooves 13, such as shown in FIGS. 1A, 1B and 10, the crimping strainsincident to expansion of the flange 14 into grooves 13 are balanced. Itis thus insured that the emissive face of the cathode cap will be andremain parallel to the opposed face of the grid or focusing electrode 18(FIG. with which the assembly is subsequently associated in a tube.

As will be understood by those skilled in the art, with the assemblyincorporated in an electronic tube, the cathode cap 17 is heated toemission temperature by heat conducted to it by the sleeve 12 in whichis disposed the usual heater element (not shown). An additional benefitof the grooved disc assembly is a substantial decrease in the contactarea between the sleeve and disc with resultant decrease in the heatlosses and a shortening of the warm-up time of the tube.

In brief rsum, so far as the tube manufacturer is concerned, the use ofgrooved ceramics in the cathode assemblies provide uniformity of cut-offcharacteristic, minimization of microphonics and reduced heater input;and so far as the cathode manufacturer is concerned, the use of groovedceramics afiords superior cathode assemblies with substantialelimination of financial losses due to cracked ceramics.

It is to be understood that either or both faces of the ceramic discsmayalso have annular shadow ridges or grooves 105 to prevent formationof leakage paths by deposits sublimed from the cathode sleeve. In suchcase and as shown in certain figures, the annular shadow grooves orridges are beyond the outer ends of the radial grooves 13. Also shownare openings intersecting the grooves 108.

What is claimed is:

1. A cathode assembly comprising a ceramic spacer disc having an openingextending therethrough between its opposite faces, at least one of saidfaces having symmetrically angularly spaced grooves extending outwardlyfrom said opening, and a cathode sleeve extending through said opening,said sleeve having a pair of embossed flanges respectively engaging theopposite faces of said disc adjacent the opposite ends of said opening,at least one of said flanges being locally depressed into said angularlyspaced grooves of the corresponding face of the disc to provide a seriesof flange keys which preclude rotation of said sleeve.

2. A cathode assembly comprising a ceramic spacer disc having an openingextending therethrough between its opposite faces, at least one of saidfaces having symmetrically angularly spaced grooves of progressivelydecreasing depth and each extending outwardly from said opening, and acathode sleeve extending through said opening and having a pair ofembossed flanges crimped against said opposite faces of the disc andinto interlocking engagement with said grooves.

3. A method of making cathode assemblies from cathode sleeves andceramic spacer discs varying slightly in thickness and in size of theirsleeve-receiving hole which comprises forming in at least one face ofthe discs symmetrically angularly spaced grooves extending outwardlyfrom the sleeve-receiving hole, embossing said sleeves to form for eachof them a pair of flanges respectively engaging opposite faces of theassociated disc adjacent the ends of its sleeve-receiving hole, andapplying crimping pressure to each pair of flanges to expand at leastone of them into the angularly spaced grooves of the corresponding faceof the associated spacer disc.

References Cited by the Examiner UNITED STATES PATENTS 2,454,326 11/48Makenny 295 12 2,530,855 11/50 Bugg et a1. 29-523 2,551,871 5/51 Briggs313270 2,717,325 9/55 Gosslar 313-270 2,978,606 4/61 Kahl 313270 FOREIGNPATENTS 1,001,771 1/57 Germany. 1,043,521 11/58 Germany.

OTHER REFERENCES RCA TN No. 306, November 30, 1959.

ROBERT SEGAL, Acting Primary Examiner.

ARTHUR GAUSS, Examiner.

2. A CATHODE ASSEMBLY COMPRISING A CERAMIC SPACER DISC HAVING AN OPENINGEXTENDING THERETHROUGH BETWEEN ITS OPPOSITE FACES, AT LEAST ONE OF SAIDFACES HAVING SYMMETRICALLY ANGULARLY SPACED GROOVES OF PROGRESSIVELYDECREASING DEPTH AND EACH EXTENDING OUTWARDLY FROM SAID OPENING, AND ACATHODE SLEEVE EXTENDING THROUGH SAID OPENING AND HAVING A PAIR OFEMBOSSED FLANGES CRIMPED AGAINST SAID OPPOSITE FACES OF THE DISC ANDINTO INTERLOCKING ENGAGEMENT WITH SAID GROOVES.